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Author Topic: Cobra 2826/12 No Power  (Read 518 times)

Online Ken Culbertson

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Cobra 2826/12 No Power
« on: January 05, 2019, 04:36:08 PM »
I have just installed a new Cobra 2826/12 in my ARF Nobler (42 oz with 4s 2200 battery).  I used the same ESC settings (Castle Phoenix 50 Lite) that I use on my 2820/12.  I run the 2820/12 on a 12 x 6 at 9300 rpm and it is a tiger.  With the same battery and same ESC the 2826/12 is an anemic kitten.  Barely enough power to do a loop.  My question is - could this be a wrong setting in the ESC?  If not then where do I start to find out what the problem is.  That motor should haul a 46 size plane like it was a feather.

Ken
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Online Crist Rigotti

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Re: Cobra 2826/12 No Power
« Reply #1 on: January 05, 2019, 06:30:35 PM »
The 2820/12 is a 970kv and the other 2826/12 is a 760kv.  There will be a big difference if you used the same settings.
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Online Ken Culbertson

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Re: Cobra 2826/12 No Power
« Reply #2 on: January 05, 2019, 07:28:38 PM »
The 2820/12 is a 970kv and the other 2826/12 is a 760kv.  There will be a big difference if you used the same settings.
I think I read somewhere that you have/had a 2826/12.  What settings should I look at?  Also, it sticks between magnets when you turn it over a whole lot more that the 2820/12.  Is this normal?

Ken
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Offline Igor Burger

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Re: Cobra 2826/12 No Power
« Reply #3 on: January 06, 2019, 01:07:04 AM »
The 2820/12 is a 970kv and the other 2826/12 is a 760kv.  There will be a big difference if you used the same settings.

So that mean if you replace motor with 970 RPM per Volt with 760 RPM per Volt, you will need 970/760 more Volts for the same RPM. That makes 970/760=1.28 more volts. That means instead of 4 cells you will need 1.28*4 = 5.12 cells. So try 5 cell battery and hopefully it will be enough.

Question is, why you want large motor on such small model. I use such motor on 60+ oz models.

Online Ken Culbertson

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Re: Cobra 2826/12 No Power
« Reply #4 on: January 06, 2019, 08:30:07 AM »
So that mean if you replace motor with 970 RPM per Volt with 760 RPM per Volt, you will need 970/760 more Volts for the same RPM. That makes 970/760=1.28 more volts. That means instead of 4 cells you will need 1.28*4 = 5.12 cells. So try 5 cell battery and hopefully it will be enough.

Question is, why you want large motor on such small model. I use such motor on 60+ oz models.
Probably inexperience.  I was led to believe that a 12 x 6 prop at about 8,500 rpm was what I needed.  The prop chart for the 2826/12 produces that (and thrust = nearly 2x the weight of the plane) from a 4s.  14.8 x 790 = 11,692 potential rpm.  8,500 should have been a walk in the park.  Obviously I have something to learn, like maybe the prop charts don't work for CL?    I have run the RPM up to 10,500 (Huben timer)  with no change in power so all I can surmise from that is something in the ESC is preventing it or I have a bad motor.  The plane was a tiger with an OS35s on a 10 x 6W.

Correct me if I am wrong here but one of the main functions of the ESC is to provide the required RPM's regardless of load and as long as the prop is turning at those RPM's it should deliver the power necessary to maintain those RPM's.

As to why the larger motor - I purchased it for a larger plane before deciding to convert the Nobler.  The Nobler is overweight and a bit nose heavy from the 4s and has no room for a 5s.  So, if nothing in the ESC can be changed and I cannot fit a 5s then I need a smaller motor to get more power.  Some IC diehards told me I was crazy to go electric.  I am starting to see why! mw~

Ken
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Offline pmackenzie

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Re: Cobra 2826/12 No Power
« Reply #5 on: January 06, 2019, 10:58:08 AM »
ESC will only hold constant RPM if you set it to governor mode and have enough battery voltage.
 Once the ESC hits full power it can't provide any additional RPM so governor stops working.

AXI 2826/10 on 4S with 12x6 will work fine, used it in a Vector 40
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Online Ken Culbertson

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Re: Cobra 2826/12 No Power
« Reply #6 on: January 06, 2019, 11:16:05 AM »
ESC will only hold constant RPM if you set it to governor mode and have enough battery voltage.
 Once the ESC hits full power it can't provide any additional RPM so governor stops working.

AXI 2826/10 on 4S with 12x6 will work fine, used it in a Vector 40
That may be the problem.  I will yank it out tonight and take it to the computer for a refresher course.  I am still not ruling out a bad motor.  It just isn't as smooth as my other three Cobra's.

Ken
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Online Ken Culbertson

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Re: Cobra 2826/12 No Power
« Reply #7 on: January 06, 2019, 06:22:59 PM »
That may be the problem.  I will yank it out tonight and take it to the computer for a refresher course.  I am still not ruling out a bad motor.  It just isn't as smooth as my other three Cobra's.

Ken
That was it.  Somehow the programming got reset to default which would be Airplane Mode.
Thanks - Ken
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Online Motorman

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Re: Cobra 2826/12 No Power
« Reply #8 on: January 09, 2019, 09:17:47 PM »
Just sayin' those prop charts are made for planes without lines and lines are allot of drag.
There will be a sunny day and we will fly our airplanes.

Online Ken Culbertson

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Re: Cobra 2826/12 No Power
« Reply #9 on: January 26, 2019, 06:55:36 PM »
ESC will only hold constant RPM if you set it to governor mode and have enough battery voltage.
 Once the ESC hits full power it can't provide any additional RPM so governor stops working.

AXI 2826/10 on 4S with 12x6 will work fine, used it in a Vector 40
Follow up - your suggestion fixed the problem.  Motor works great now. 5.2 laps on 9000 rpm.  Flys better than it did on IC.

Ken
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